oracle database limits

Here is the  limitation of oracle database

Physical Database Limits

Item	Type of Limit	Limit Value
Database Block Size	Minimum	2048 bytes; must be a multiple of operating system physical block size
	Maximum	Operating system dependent; never more than 32 KB
Database Blocks	Minimum in initial extent of a segment.	2 blocks
	Maximum per datafile	Platform dependent; typically 222 - 1 blocks
Controlfiles	Number of control files	1 minimum; 2 or more (on separate devices) strongly recommended
	Size of a control file	Dependent on operating system and database creation options; maximum of 20,000 x (database block size)
Database files	Maximum per tablespace	Operating system dependent; usually 1022
	Maximum per database	65533 May be less on some operating systems Limited also by size of database blocks and by the DB_FILESinitialization parameter for a particular instance
Database extents	Maximum per dictionary managed tablespace	4 GB * physical block size (with K/M modifier);4 GB (without K/M modifier)
	Maximum per locally managed (uniform) tablespace	2 GB * physical block size (with K/M modifier);2 GB (without K/M modifier)
Database file size	Maximum	Operating system dependent. Limited by maximum operating system file size; typically 222 or 4 MB blocks
MAXEXTENTS	Default value	Derived from tablespace default storage or DB_BLOCK_SIZE initialization parameter
	Maximum	Unlimited
Redo Log Files	Maximum number of logfiles	Limited by value of MAXLOGFILES parameter in the CREATE DATABASE statement  Control file can be resized to allow more entries; ultimately an operating system limit
	Maximum number of logfiles per group	Unlimited
Redo Log File Size	Minimum size	50 KB
	Maximum size	Operating system limit; typically 2 GB
Tablespaces	Maximum number per database	64 KB Number of tablespaces cannot exceed the number of database files, as each tablespace must include at least one file
Bigfile Tablespaces	Number of blocks	232 (4 GB) blocks
Smallfile (traditional) Tablespaces	Number of blocks	222 (4 MB) blocks

Logical Database Limits

Item	Type			Limit
GROUP BYclause	Maximum length			The GROUP BY expression and all of the nondistinct aggregate functions (for example, SUM, AVG) must fit within a single database block.
Indexes	Maximum per table			Unlimited
	total size of indexed column			75% of the database block size minus some overhead
Columns	Per table			1000 columns maximum
	Per index (or clustered index)			32 columns maximum
	Per bitmapped index			30 columns maximum
Constraints	Maximum per column			Unlimited
Subqueries	Maximum levels of subqueries in a SQL statement			Unlimited in the FROM clause of the top-level query  255 subqueries in the WHERE clause
Partitions			Maximum length of linear partitioning key	4 KB - overhead
			Maximum number of columns in partition key	16 columns
			Maximum number of partitions allowed per table or index	64 KB - 1 partitions
Rows			Maximum number per table	Unlimited
Stored Packages			Maximum size	PL/SQL and Developer/2000 may have limits on the size of stored procedures they can call. The limits typically range from 2000 to 3000 lines of code.  See Also: Your PL/SQL or Developer/2000 documentation for details
Trigger Cascade Limit			Maximum value	Operating system-dependent, typically 32
Users and Roles			Maximum	2,147,483,638
Tables			Maximum per clustered table	32 tables
			Maximum per database	Unlimited

Process and Runtime Limits

Item	Type	Limit
Instances per database	Maximum number of cluster database instances per database	Operating system-dependent
Locks	Row-level	Unlimited
	Distributed Lock Manager	Operating system dependent
SGA size	Maximum value	Operating system-dependent; typically 2 to 4 GB for 32-bit operating systems, and 4 GB for 64-bit operating systems
Advanced Queuing Processes	Maximum per instance	10
Job Queue Processes	Maximum per instance	1000
I/O Slave Processes	Maximum per background process (DBWR, LGWR, etc.)	15
	Maximum per Backup session	15
Sessions	Maximum per instance	32 KB; limited by the PROCESSES and SESSIONS initialization parameters
Global Cache Service Processes	Maximum per instance	10
Shared Servers	Maximum per instance	Unlimited within constraints set by the PROCESSES and SESSIONS initialization parameters, for instance
Dispatchers	Maximum per instance	Unlimited within constraints set by PROCESSES and SESSIONS initialization parameters, for instance
Parallel Execution Slaves	Maximum per instance	Unlimited within constraints set by PROCESSES and SESSIONS initialization parameters, for instance
Backup Sessions	Maximum per instance	Unlimited within constraints set by PROCESSES and SESSIONS initialization parameters, for instance

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